From 5de834cb82dda51dec26c8b829d2b602a446d88b Mon Sep 17 00:00:00 2001 From: whitequark Date: Sat, 3 Aug 2019 23:57:50 +0000 Subject: [PATCH] back.rtlil: use a dummy wire, not 'x, when assigning to shorter LHS. Using 'x is legal RTLIL, in theory, but in practice it crashes Yosys and when it doesn't, it causes Yosys to produce invalid Verilog. Using a dummy wire is always safe and is not a major readability issue as this is a rare corner case. (It is not trivial to shorten the RHS in this case, because during expansion of an ArrayProxy, match_shape() could be called in a context far from the RHS handling logic.) --- nmigen/back/rtlil.py | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/nmigen/back/rtlil.py b/nmigen/back/rtlil.py index 6ef0d86..ac2b99f 100644 --- a/nmigen/back/rtlil.py +++ b/nmigen/back/rtlil.py @@ -578,9 +578,9 @@ class _LHSValueCompiler(_ValueCompiler): elif new_bits < value_bits: return self(ast.Slice(value, 0, new_bits)) else: # new_bits > value_bits - # It is legal to assign to constants on LHS in RTLIL; such assignments are ignored. dummy_bits = new_bits - value_bits - return "{{ {}'{} {} }}".format(dummy_bits, "x" * dummy_bits, self(value)) + dummy_wire = self.s.rtlil.wire(dummy_bits) + return "{{ {} {} }}".format(dummy_wire, self(value)) def on_Signal(self, value): if value not in self.s.driven: -- 2.30.2